Suspense and survival in Child 44, by Tom Rob Smith

How do you fix the mistakes in your life? When you are Leo Demidov, a disgraced member of the Soviet MGB and you are responsible for capturing, sentencing and killing untold numbers of regular people, people who are just trying to survive under Joseph Stalin’s oppressive regime, the question is hard to answer. Leo’s epiphany comes late. His wife, Raisa already hates him. He’s been demoted to the militia, a low-level assignment. He’s lost his privileges and has more than a few enemies. Leo and Raisa have almost nothing. They can only survive by staying together.

Someone is murdering young children, leaving their bodies to be discovered. The government claims to solve the murders as individual cases, but Leo sees a pattern and he knows someone is still out there, planning another attack.